Will This Float Your Boat - 6

Sea level rise is real.

The calculation of how, when, and why Sea Level Rise (SLR) takes place is easy to assume, but it is best done by using existing data, while realizing that "climate change" means that the data will change as the climate changes.

In other words, don't make projections of the climate by expecting the same history we have now to show up as the climate of the future.

Sea level rise was discussed in the last post of this series with existing data, projecting those data into the future, but, not assuming the same rate of SLR.

In other words, acceleration of the percent of SLR.

I want to fine tune that in this post, by applying various acceleration rates to various sections of Greenland and West Antarctica, projecting acceleration of melt, and therefore SLR, based on sections or zones in those locations that are substantially different.

In other words, I will be applying a faster acceleration where appropriate, but also applying a slower acceleration rate where appropriate.

The map of Greenland (Fig. 1) for example, shows these hypothetical sections or zones where different melt quantities take place.

Those sections or zones are labelled "Coastal", "Inland1", "Inland2", and "No Melt".

The lines depicting them are not to exact scale (the ice sheet varies in thickness, so the lines which outline those zones illustrate a contemplation of quantity of ice, not quantity of land).

Fig. 1 Click on map to Enlarge

Accordingly, the rate-of-melt graph (Fig. 3) is based on the ongoing melt of the Greenland and West Antarctica ice sheets, graphed according to the individual melt rate of those zones.

Remember that the fundamental basis or cause, of the melt acceleration values, derive from our current knowledge.

We know that a combined 500 km³ (500 cubic kilometers) of ice is lost to melt each year (75% Greenland / 25% W. Antarctica).

That amount was determined by CryoSat-2, a satellite that has one mission.

That mission is to measure the ice volume of Greenland and West Antarctica, which allows us to determine the rate of melt as the ice sheet volume decreases over time (see the previous post in this series here).

In the software that generates the graph (Fig. 3), I have added a list of acceleration rates as follows: coastal = 0.1487, inland1 = 0.10, inland2 = 0.0437, and insignificant = 0.0408), which relate to the stages of melt, proceeding from fast melt zones such as "Coastal," on to the "No Melt" zone ("No Melt" means not melting prior to 2100 in any significant amount).

As CryoSat-2 informs us of further changes, or the regions or zones are better understood, all I have to do is change those values in the software, then regenerate the graph.

For Greenland, (Fig. 1) 21.49 ft. is the maximum global SLR if all ice melts, and the sections or zones are as follows:

No Melt = 8.596 ft. SLR (40% of total ice sheet)
Inland2 = 6.447 ft. SLR (30% of total ice sheet)
Inland1 = 4.298 ft. SLR (20% of total ice sheet)
Coastal = 2.149 ft. SLR (10% of total ice sheet)

Fig. 2 Click on map to Enlarge

The "Coastal" zone is the fastest melting, with a potential SLR of 2.149 ft., constituting 10% of the total ice sheet.

The hardest to melt, the "No Melt" zone, furthest from the coast, is estimated to be 40% of the total ice sheet.

For W. Antarctica, (Fig. 2) 26.44 ft. is the maximum global SLR if all ice there melts.

The sections or zones are:

No Melt = 10.576 ft. SLR (40% of total ice sheet)
Inland2 = 7.932 ft. SLR (30% of total ice sheet)
Inland1 = 5.288 ft. SLR (20% of total ice sheet)
Coastal = 2.644 ft. SLR (10% of total ice sheet)

Note that for both polar ice sheets, the "ft. SLR" values represent the potential global SLR from each zone, if all ice melts in that particular zone.

The percentages for both ice sheets concern near term melt, which is defined as taking place now, as well as taking place before 2100.

Fig. 3 Click on graph to Enlarge

The combined values concept on the graph (green line) represents the actual total melt taking place currently in both places when added together.

Obviously Greenland and W. Antarctica are both melting at the same time, now, but it is not so obvious that they are melting under very different circumstances and rates for SLR generation.

Currently, the ice melt rate (500 km³) is based on volume of ice melt in Greenland (375 km³) and Antarctica (125 km³) which shows that Greenland is melting much faster.

That will change and is changing as the Coastal ice diminishes, and the slower melting zones kick in.

For example, the graph shows Greenland's coastal (fast melt zone) ice melting by about 2048, the same year it shows total sea level rise reaching three feet (decades before the IPCC projected date of ~2100), while W. Antarctica is still in the coastal-ice-melt phase (20 Big U.S. Cities that Should Worry About Sea Level Rise).

The 75% / 25% ratio will become 50% / 50% and later 25% / 75% over time.

In conclusion, I realize that the amounts of today's post are not the same as the previous post.

There are more zones and more rates in the software now, and today's graph does not extend all the way out to 2100 as the previous ones did.

No need to, because the SLR shown in Fig. 3 is a warning and wake-up call for coastal cities in the sense that an SLR of 2-3 ft. by 2044-48 means a severe crisis, and they know it (cf. Scientific American).

The surge mentioned in the previous post, which happened near NYC, is another red flag, because it is another indication that unexpected developments can take place "quickly."

So, I have made the software flexible enough to stumble along with surprises as they take place.

All suggestions appreciated.

The next post in this series is here, the previous post in this series is here.